A method using a GPS (Global Positioning System) signal emitted from a GPS satellite is one of most widely propagated position determination techniques. However, the method using a GPS signal has its limits since they cannot be used in locations where satellite signals cannot be received such as tunnels and indoors. Therefore, a location determination technique using a WLAN (Wireless Local Area Network) is being developed as a supplementary technique.
A technique has been proposed by Skyhook as one of the position determination methods using a WLAN signal. This technique uses dedicated user terminals to collect information of APs installed all over and then builds a database with MAC addresses and RSSI (Received Signal Strength Indication) values. If a position recognition program of Skyhook is executed at a computer, a coordinate is calculated, and then the coordinate is input to a map, so that the position is displayed on the map. The position-based service of Skyhook has been spotlighted as terminals capable of supporting WLAN connection such as smart phones and notebooks are put into the market. The position information system of Skyhook collects RF fingerprints while moving by using a scanning vehicle. However, since the technique of Skyhook employs a method of measuring AP signals while scanning the mad by using a vehicle, it has a disadvantage of not being able to use indoors.
As another technique, Microsoft has proposed a RADAR method. In the RADAR method, a RF pattern of each point along a passage is collected indoors, and a database is built with the RF pattern so that a position is determined by comparing the collected RF pattern with an RF pattern proposed by a MD of the user. A margin of error is 2 to 3 meters. This technique should satisfy the premise that an accurate position of the AP should be known. For example, 70 points are measured in a 22.5 m×43.5 m mom size, and each point is measured 20 times per AP so that the measurement data is used for providing position information. An interior plan is provided and a wall attenuation coefficient is applied. Different from the technique of Skyhook, the technique of Microsoft may provide indoor position information. However, since reference data for position determination is collected through direct tours and indoors visits, it is inevitable that a large amount of time and costs are needed for such a large-scale service.
The above techniques should collect reference data for position determination through tours and visits to service areas because the service provider is not a communication service provider and so data for AP signals cannot be directly obtained. However, if the service provider is a communication service provider which provides WLAN service, data for AP signals will be obtained more conveniently and economically.